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-rw-r--r--Documentation/power/runtime_pm.txt10
-rw-r--r--drivers/base/power/runtime.c18
2 files changed, 26 insertions, 2 deletions
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 6066e3a6b9a9..d3710dc6d25f 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -782,6 +782,16 @@ will behave normally, not taking the autosuspend delay into account.
Similarly, if the power.use_autosuspend field isn't set then the autosuspend
helper functions will behave just like the non-autosuspend counterparts.
+Under some circumstances a driver or subsystem may want to prevent a device
+from autosuspending immediately, even though the usage counter is zero and the
+autosuspend delay time has expired. If the ->runtime_suspend() callback
+returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is
+in the future (as it normally would be if the callback invoked
+pm_runtime_mark_last_busy()), the PM core will automatically reschedule the
+autosuspend. The ->runtime_suspend() callback can't do this rescheduling
+itself because no suspend requests of any kind are accepted while the device is
+suspending (i.e., while the callback is running).
+
The implementation is well suited for asynchronous use in interrupt contexts.
However such use inevitably involves races, because the PM core can't
synchronize ->runtime_suspend() callbacks with the arrival of I/O requests.
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index acb3f83b8079..6a7f7b06968f 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -285,6 +285,9 @@ static int rpm_callback(int (*cb)(struct device *), struct device *dev)
* If a deferred resume was requested while the callback was running then carry
* it out; otherwise send an idle notification for the device (if the suspend
* failed) or for its parent (if the suspend succeeded).
+ * If ->runtime_suspend failed with -EAGAIN or -EBUSY, and if the RPM_AUTO
+ * flag is set and the next autosuspend-delay expiration time is in the
+ * future, schedule another autosuspend attempt.
*
* This function must be called under dev->power.lock with interrupts disabled.
*/
@@ -396,10 +399,21 @@ static int rpm_suspend(struct device *dev, int rpmflags)
if (retval) {
__update_runtime_status(dev, RPM_ACTIVE);
dev->power.deferred_resume = false;
- if (retval == -EAGAIN || retval == -EBUSY)
+ if (retval == -EAGAIN || retval == -EBUSY) {
dev->power.runtime_error = 0;
- else
+
+ /*
+ * If the callback routine failed an autosuspend, and
+ * if the last_busy time has been updated so that there
+ * is a new autosuspend expiration time, automatically
+ * reschedule another autosuspend.
+ */
+ if ((rpmflags & RPM_AUTO) &&
+ pm_runtime_autosuspend_expiration(dev) != 0)
+ goto repeat;
+ } else {
pm_runtime_cancel_pending(dev);
+ }
} else {
no_callback:
__update_runtime_status(dev, RPM_SUSPENDED);